1. Field of the Invention
This application relates to a novel class of oligomers having acetylene terminal groups in general and more particularly to the preparation of polymerizable acetylene-substituted tetraimines.
2. Prior Art
The need for prepolymers and oligomers which polymerize into thermally stable, mechanically strong thermoset resins with the production of little or no voids has been thoroughly established. Such materials are useful as adhesives, molding compounds, insulating materials and as matricies in the formation of composites.
During the past ten years considerable resources have been expended in the field of acetylene chemistry in an attempt to provide thermally stable materials which polymerize into useful resins having little or no voids. The closest known prior art, disclosing this work is found in the following series of U.S. Patents issued to Co-applicant, Norman Bilow, herein and others. The relevant U.S. Patents are: U.S. Pat. Nos. 3,845,018, entitled "Acetylene Substituted Polyimide Oligomers," dated Oct. 29, 1974; 3,864,309, entitled "Copolymer of Polyimide Oligomers and Terephthalonitrile N,N-Dioxide and Their Method of Preparation," dated Feb. 4, 1975; 3,879,349, entitled "Homopolymerization of Acetylene Substituted Polyimide Polymers," dated Apr. 22, 1975; 3,928,450, entitled "Acetylene Substituted Aromatic Primary Amines and the Process of Making Them," dated Dec. 23, 1975; 4,075,111, entitled "Heavy Metal Chalcogenide-Polyimide Lubricative Composites," issued Feb. 21, 1978; 4,098,767, entitled "Copolymers of Ethynyl Terminated Polyimides and Diethynylbenzene," issued July 4, 1978; and 4,108,836, entitled "Process for Synthesizing Acetylene Substituted Polyimides and Polyimides Thereof," issued Aug. 22, 1978.
Each of the patents listed above and incorporated herein by reference disclose inventions relating to acetylene terminated polyimides or various combinations employing polyimides. The principal disadvantage of the oligomers, polymers and copolymers disclosed in these patents lies in their relatively high melting points which renders them difficult to process and in the high cost of the materials.
The results of similar studies of high temperature polyimides which are not acetylene terminated are disclosed in U.S. Pat. No. 3,897,395, issued to Gaetano Francis D'Alelio for "Chain-Extending Functional Polyimides by Dipole Reactions" in July of 1975. The materials of the "395" D'Alelio Patent are fairly characterized as intractable and very difficult to process.
Applicants are unaware of any polymeric resins which cure through addition reactions without the production of void producing gasses that are easily prepared, exhibit long pot lives and exhibit good stabilities at high temperatures. Accordingly, it is an objective of this invention to provide a new family of prepolymers which can be cured into thermoset resins by addition reactions.
A second purpose of this invention is to provide a family of heat resistant plastics.
A third purpose of this invention is to provide a family of very easily synthesized thermosetting prepolymers.
A fourth purpose is to provide a family of thermosetting prepolymers in which the imine moiety is conjugated with at least one adjacent aromatic ring, since this type of structure enhances thermal stability.
A fifth objective of this invention is to provide diimines or polyimines which contain two or more acetylene terminal groups.
A sixth objective of this invention is to provide curable prepolymers suitable for use in manufacturing laminates, molding compounds, lubricative solid composites, structural composites, etc.